Method and device for determining the pick-up position of electrical components in a component in a components placement device

ABSTRACT

A device and appertaining method for picking up devices in a component placement device permits even very small components and even a first component of a new belt to be picked up by scanning the structural features of the belt directly in the proximity of the components. The positional tolerances can be disregarded so that even the first component of a new belt can be reliably detected by the pick-up tool.

[0001] The invention relates to a method and a device for determining the pick-up position of electrical components in a component placement device for populating substrates with the components, which are made ready in pockets of at least one belt, the belt being inserted into a feed module which delivers the components to a pick-up point in a defined pick-up position.

[0002] Feed modules of this type are usually provided with a pin wheel which, with its radially projecting pins, engages in transport holes in the belt and which is rotated in defined angular steps corresponding to the pitch spacing of the pockets in the belt. The pockets have a defined positional relationship with the transport holes. Fitted to the feed modules at the end of the production process, in the area of the pick-up point, are centering marks which have a defined positional relationship with the pins of the pin wheel and which are intended to compensate for production tolerances.

[0003] The feed modules are fixed in a defined position to a component table. Since the centering means for this purpose can be provided only at some distance from the pick-up points, it is possible for positional deviations to occur in the centering marks. A component placement head for handling the components is provided with the CCT camera, which is used to determine the exact position of the substrate to be populated in the component placement device. In order to be able to take into account the aforementioned positional deviations, it is usual, following the installation of the feed module, to determine the position of the centering marks on the feed module by means of this printed circuit board camera, with which, because of the defined positional relationships, the position of the component to be picked up can also be determined. Deviations in the drive system caused by operation cannot be eliminated completely in this case.

[0004] In the course of modern technologies, the components to be placed are being increasingly miniaturized. It is usual to provide the component placement head with a suction gripper, which is set down on the components to be picked up and sucks up the latter at its end. Here, the gripper has to dip into the pocket in order to be placed on the component. The permissible tolerances between the transport hole and the pocket are so great that the suction gripper making the pick-up cannot with certainty be set exactly onto the component to be picked up, and is placed on the edge of the pocket and, as a result, misses the component. In this case, however, this is a systematic error, at least over a relatively long section of the belt.

[0005] It is usual, in the case of each of the components picked up, to measure their position with respect to the suction gripper and to place the component onto the substrate with a corresponding correction value. In order to be able to determine the systematic error, at least after a belt change, a series of components was removed from the start of the belt and measured, and an average deviation was determined. However, this is a problem when the component is not found during the first attempt at a pick-up. The gripper then has to be moved step by step over the aforementioned tolerance range until it finds the component.

[0006] The invention is based on the object of accelerating the determination of the pick-up position of the components.

[0007] This object is achieved by the invention as claimed in claim 1. The structural features associated with the pockets, for example the edges of the pockets, are now independent of the positional relationship with respect to the transport holes and the centering marks. The scanning optics has such a large field of view that, even with the first setting, it safely finds the pocket and its surrounding area.

[0008] The position-resolving scanning optics transmits the measured values to the electrical evaluation unit, which calculates the accurate center position of the pockets from the appropriate data. The suction gripper can then immediately be aligned reliably on the component to be picked up.

[0009] All the positional tolerances between the component placement device and the centering marks and between the centering marks and the transport pins and between the transport pins and the pockets are therefore unimportant, and the suction gripper can be aligned with the center of the component with high accuracy without a failed attempt. The component is then removed reliably. The placement operation can then begin without further time delay.

[0010] The belts and the components can have very variable optical characteristics. For example, the belts can consist of transparent material. For this reason, it may be necessary to select different structural features, depending on the type of belt.

[0011] Advantageous developments of the invention are identified in the subclaims.

[0012] The development as claimed in claim 2 is suitable in particular for transparent belts, with which the component has a sufficient contrast. Although the components lie in the pocket with play, so that exact calibration is not immediately possible, the play is low as compared with the dimensions of the component, so that here, too, the component can be found with sufficient reliability. The precise position of the pockets can be determined with the aid of statistical methods in the case of optical measurement.

[0013] The development as claimed in claim 3 makes it possible to measure the position of the pocket exactly. This is made easier by the fact that, as a rule, the first pockets in a belt are left free of components.

[0014] It is particularly beneficial in this case to determine the edges of the pockets, as claimed in claim 4. In particular in the case of very small components, it is usual to punch the pockets out of a flat material and to close them at the bottom by means of a film. These punched pockets have sharp defined edges, which represent structural features that can be distinguished easily.

[0015] The development as claimed in claim 5 makes it possible to adjust the illumination of the structural features to different conditions, as is also done when scanning centering marks on the substrates. The illumination makes it possible to illuminate the pockets from different directions at different angles and with different wavelengths, so that the structural features can stand out optimally.

[0016] The device as claimed in claim 6 makes it possible to register the different structural features of the various belt types automatically, each full belt which differs from the others in terms of its optical and geometric characteristics being assigned to its own type.

[0017] The adaptation module as claimed in claim 7 permits optimal adaptation to the different optical conditions of the belts.

[0018] In the following text, the invention will be explained in more detail using an exemplary embodiment illustrated in the drawing.

[0019]FIG. 1 shows a side view of a component placement head and a feed module in a component belt,

[0020]FIG. 2 shows a plan view of the feed module according to figure 1.

[0021] According to FIGS. 1 and 2, a strip-like belt 1 is provided with lateral transport holes 2 and pockets 3 for components 4 laid therein and is inserted into a disk-like flat feed module 5 which is fixed in a defined position in the range of movement of a component placement head 6 of a component placement device. The feed module 5 has a pin wheel 7 which can be driven step by step and has transport pins 8 which stand out peripherally and engage without play in the transport holes 2 in the belt 1. The positional relationship between the pockets and the transport holes is defined by relevant standards. However, the permissible tolerances here are virtually as great as the lateral dimensions of the smallest components.

[0022] On its underside, facing the belt, the component placement head has a suction gripper 9 and scanning optics 10 in the form of a CCT camera, whose objective is surrounded by an illuminating means 11 which illuminates the field of view of the scanning optics 10. The illuminating means 11 can, for example, comprise a large number of light-emitting diodes of different wavelengths and different orientations. Matching the various belt types, it is possible to activate a beneficial selection of the diodes in such a way that the structural features stand out with good contrast and can be detected reliably.

[0023] The scanning optics 10 is aimed at a pick-up point 12 of the components in the feed module 5. It is capable of detecting structural features 14, for example the edges of an empty pocket. It is connected to an image evaluation unit 13, in which the central position of the pocket 3 is calculated by using this data, so that the following component 4 can be gripped reliably by the suction gripper, all the tolerances being eliminated.

[0024] Over a relatively long section of the belt, the position of the pocket 3 in relation to the transport hole can change. In a further optical scanning unit, not illustrated, the position of the components removed on the suction gripper 9 is measured accurately in order to increase the placement accuracy. In this way, the sliding positional change of the pockets can be registered reliably and taken into account during operation in such a way that remeasurement of the belt (1) with the aid of the scanning optics 10 might only be required following a loss of data on the component placement device, for example following an interruption. 

1. A method of determining the pick-up position of electrical components (4) in a component placement device for populating substrates with the components (4), which are made ready in pockets (3) in at least one belt (1), the belt (3) being inserted into a feed module (5), which delivers the components (4) to a pick-up point (12) in a defined pick-up position, the components (4) being removed from the pockets (3) by means of a freely positionable component placement head (6), position-resolving scanning optics (10) of the component placement head (6) being moved over centering marks in the area of the pickup point (12) and determined with the aid of an image evaluation unit (13) belonging to the component placement device, characterized in that the scanning optics (10) is aimed at structural features (14) that are associated directly with the pockets (3) and which are used as the centering marks, and in that the image evaluation unit (13) calculates the average position of the pockets (3) from the position of the structural features (14).
 2. The method as claimed in claim 1, characterized in that the component (4) lying in the pocket (3) is scanned.
 3. The method as claimed in claim 1, characterized in that the structural features of the pocket (3) are scanned directly.
 4. The method as claimed in claim 3, characterized in that the edges of the pocket (3) are detected.
 5. The method as claimed in one of the preceding claims, characterized in that the scanning optics (10) is assigned an illuminating means (11), whose variable optical characteristics are adapted to different belt types.
 6. A device for carrying out the method as claimed in one of the preceding claims, characterized in that a control unit belonging to the component placement device contains control means for positioning the scanning optics over the pocket (3), in that type data about the component belt can be transmitted to the control unit, in that the scanning optics (10) can be moved over the structural features of the belt (1) by using the type data and in that the image evaluation unit (13) is equipped with means for detecting and processing different structural features of the various belt types.
 7. The device as claimed in claim 6, characterized in that the image evaluation unit (13) and a control system for the illuminating means (11) are connected to a self-teaching adaptation module, which adjusts the illumination (11) to a sufficient contrast effect of the structural features. 